Apparatus for growing aerobic organisms



Sept. 19, 1950 v s, T H IETAL I 2,522,947

APPARATUS FOR GROWING AEROBIC ORGANISIIS Original Filed May 16, 19 45 INVENTOR RAYMOND S. HATCH AND RICHARD N. HAMMOND bottoms of the tanks.

Patented Sept. 19, 1950 j UNITED STATES PATENT OFFICE.

APPARATUS FOR GROWING AEBOBIO ORGANISMS Raymond .8. Batch and Richard N. Hammond, Longview, Wash, assignors to Weyerhaenser Timber Company, Longview, Wash, a corporation of Washington Original application May 16, 1945, Serial No. 594,082. Divided and thi application March 2'1, 1947, Serial No. 737,616

1 Claim. 1

organisms mentioned, has, for many years, followed certain conventional practice involving the aeration, in suitably constructed tanks, of a liquid substrate by forcing air through perforated pipes or diffusing elements disposed in the The amount of air which can be forced through a liquid substrate in conventional yeast propagating equipment is, to a large extent, limited by foaming conditions and by the power required to force air under a substantial headthrough the layer of liquid. Furthermore, it is general practice to use a foamdispersing agent such as a fat or oil to limit excessive foam formation. These foam-dispersing agents tend to contaminate the yeast and add to the cost of yeast production. Furthermore, because it is not possible economically to force the required amount of air through the substrate to obtain ideal rates of growth, the time required for growth is relatively long, and a large tank capacity is necessary when large production is required.

It is the object of the present invention to provide an apparatus for accelerating the growth of aerobic organisms, thereby facilitating production for commercial purposes.

Another object of the invention is the provision of an apparatus for propagating aerobic organisms with a minimum ofpower input and consequent operating cost.

A further object of the invention is the provision of an apparatus in which large quantities of air are intimately mixed with the substrate and the use of oily foam-dispersing agents is avoided.

Other objects and advantages of the invention will be apparent as it is better understood by reference to the following specification and the accompanying drawing, in which:

Fig. l is a vertical section through an apparatus suitable for the practice of the invention; and

Fig. 2 is a horizontal section on the line 2-2 of Fig. 1.

' in the tank 5 surrounding the draft tube.

Referring to the drawing, 5 indicates a suitable receptacle or tank,.preferably of cylindrical form. Within the tank 5, a second receptacle or draft tube 6 is supported. The crosssectional area of the draft tube 6 is preferably a proximately one-half the cross-sectional area o the tank 5. The lower end of the draft tube 6:15 :constrlcted to an opening in which a propeller I is disposed. The propeller is mounted on a shaft 8 extendin through a gland 9 in the bottom IU of the tank 5. The shaft 8 may be driven by a motor ll directly connected thereto or by any other suitable driving mechanism.

An inlet pipe I: controlled by a valve 13 is provided for the purpose of introducing the substrate with the necessary inoculum and nutrients. An outlet pipe l4, controlled by a valve I5, is connected to the bottom of the tank 5 to permit withdrawal of the substrate after the organism has been propagated therein. A pipe I6 extends to a pointvnear the bottom of the draft tube 6 for the purpose of introducing fresh air which may be supplied by a blower (not shown) or in any other suitable manner. Since it may be desirable to reduce the temperature of the substrate during propagation of the organism, a coil Il may be provided on the inner wall of the tank 5 and supplied with any suitable cooling medium through a pipe l8 controlled by a valve IS. The cooling medium escapes through a pipe 20. The cooling coil is not, however, essential in all operations and may be eliminated.

In the operation of the apparatus as described, a liquid substrate is delivered to the tank 5, together with the necessary inoculum and nutrients, to approximately the level indicated by the dotted line, m:c, that is, to a level of approximately one-quarter of the full depth of the tank 5. The propeller I is then started. The blades are set to force the liquid downwardly and outwardly as indicated by the arrows. The rapid revolution of the propeller draws the liquid down-' wardly from the draft tube 6 and raises the level As soon as this result is effected, large quantities of air are drawn through the draft tube and forced into the substrate in the tank 5, so that the organisms in the substrate are supplied with the necessary oxygen at a rapid rate. Considerable foaming results. The foam rises in the annular space between the draft tube 6 and the wall of the tank 5 until it reaches the top of the draft tube. It then spills over the top of the draft tube and returns by gravity to the propeller at the base thereof. As the mixture of foam and liquid cascades in a thin layer down the inside I 3 wall of the draft tube 6, much of the foam breaks and disappears before it reaches the propeller.

The air at low pressure, introduced through the pipe 16, ensures the presence of an ample supply of air to be mixed with the substrate in the manner hereinbefore described. It also sweeps out of the interior of the draft tube 6 any gaseous products of metabolism resulting from the growth of the organism. If it is desirable to control the temperature of the substrate within optimum growing conditions, such control can be effected readily by supplying a suitable cooling agent at the proper temperature through the pipe I8. In many operations, such cooling is unnecessary.

When the desired propagation has been effected, the substrate can be withdrawn through the pipe I and subjected to centrifugal action for the removal of a concentrated yeast slurry. Fresh substrate, with the necessary inoculum and nutrients, can then be introduced so that the operation is repeated.

In the propagation of certain types of yeast, the growth is so rapid that the apparatus described may be operated in a, semi-continuous manner. In such operation, after growth has been started, approximately one-quarter of the substrate is withdrawn at the end of each hour and replaced by fresh substrate containing the necessary nutrients. The substrate withdrawn is subjected to centrifugal action for the removal of a concentrated yeast slurry. After another hour, a similar proportion of the substrate is withdrawn and replaced with fresh material.

The apparatus may also be used in a fully continuous operation, provided the original charge of substrate and inoculum is first allowed as suflicient growth period to develop an active growth of the organism. It is then possible to add a continuous stream of fresh substrate containing the proper nutrients at a fixed rate through the pipe l2 and atthe same time withdraw the substrate containing the organism at the same rate at which it is being added through the pipe I4. Under such operating conditions, there is a slight loss in yield; but when operating with waste materials such loss is frequently advisable to avoid excessive investment in equipment.

The apparatus as described affords a substantial improvement in the propagation of yeasts and the like, particularly in respect to the time required. Where, under the conventional methods, growth will normally require periods of from twelve to forty-eight hours, the improved method reduces the time 'of growth to about one-third of that otherwise necessary. It is possible, moreover, to work with solutions of much higher nutrient concentration because of the much more rapid utilization. of atmospheric oxygen in the method described. The apparatus also effects a material saving in power consumption, since the operation of the propeller requires much less power than is needed to blow similar quantities of air through the'substrate. In describing the apparatus, we have given certain dimensional relationships of the different elements, but the invention is not confined thereto, and various changes may be made in the details of the apparatus and in the method of procedure without departing from the invention or sacrificing the advantages thereof.

We claim:

In an apparatus for improving the propagation of aerobic organisms, an outer receptacle, an inner receptacle having a closed vertical wall with a lip below the level of the upper edge of the outer receptacle and a semi-spherical bottom with an opening centrally disposed therein, a power-driven propeller mounted in the opening, an air tube having its discharge end positioned within the inner receptacle, substantially at the center thereof and at a point contiguous to the propeller, valve-controlled pipes for introducing liquid to and for withdrawing liquid from the outer receptacle, and a coil for the passage of cooling liquid in the space between the verticallyextending walls of the inner and outer receptacles.

RAYMOND S. HATCH. RICHARD N. HAMMOND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 328,585 Hornbostel Oct. 20, 1885 1,876,994 Mann Sept. 13, 1932 1,982,002 Hatch Nov. 27, 1934 2,111,726 Plews Mar. 22, 1938 2,244,902 Stich June 10, 1941 2,298,561 Hendrickson Oct. 13, 1942 

